Method and anode for electrodeposition of rust-resisting coatings



'' straight zinc. V

zinc can be deposited per unit of current Patented Sept. 29,

UNITED STATES 1,555,537 [PATENT oration.

CHRISTIAN JOHN wnnnmmn, or TQTTENVILLE, EW YORK, ASSIGNOZR TO THE nons- SLER & nnssnncnnn. CHEMICAL COMPANY, OF NEW YORK, 11. in, A conronarron OF NEW YORK.

METHOD ANDQANIO'DE non nnncrnonnrosrrron or nnsnnnsrs'rme GOA'IIIIINGSQ No Drawing.

To all whom it may concern:

Be it known that I, CHRISTIAN JOHN WERNLUND, a citizen of the United States, and resident of Tottenville, in the county of Richmond and State of New York, have invented certain" new and useful Improvements in Methods and Anodes for Electrodeposition of Rust-Resisting Coatings, of which the following is a specification.

My invention relates in general to the electroplating on iron and steel or other metalarticles of alloys of cadmium and mercury.

Cadmium has many properties which ren.--

der it advantageous Over other metals and alloys as a protective coating for metals such as iron and steeL. Itis light in color and has a higher solution potential than iron, thus tending to protect the iron from corrosion. As its solution potential is higher than that of iron and lower'than that of zinc, the same weight of protective coat ing of cadmium affords more protection to atmospheric corrosion than is afforded by Also more cadmium than used. The oxide coating formed by atmospheric or other corrosion of cadmium is thinner and more adherent than that formed on zinc, consequently the tendency of cadmium to scale off and waste away is much less pronounced than that of zinc.

While I have found that pure cadmium coatings can be eifectively deposited electrolytically, I have further found that alloy coatings comprising cadmium retain in large measure the advantageous features of pure cadmium coatings in durability and rapidity of deposit and can be much more cheaply and conveniently produced than previous coatings of pure cadmium, According to my invention, I produce alloyed coatings comprising over 2% of cadmium and another metal, such as cadmium and mercury or zinc, or zinc, cadmium and mercury, using either plain anodes with a suitable bath, or alloy anodes, or both. The coatings have the enhanced practical advantages characteristic of pure cadmium coatings in giving better protection than zinc with less thickness, good color of coating, and economy of current. The advantage of using mercury in combination with cadmium or are as follows:

Application filed January 5, 1924. Serial No, 684,506.

' zinc and cadmium is that the resultant The cathode po-- Such a coating may be formed by the use of a plating solution to which the proper addition of cadmium or cadmium and mercury compounds soluble in the bath have been made, or the metals can be furnished to the solution by the use of cadmium anodes or alloy anodes. Examples of the scope of this Example I.

To platesteel articles such asstamp'ings' invention for aeroplane parts, I may proceed as follows The parts are first cleaned, preferabl' by sand blasting until all of thescale and oose dirt are removed. They are then put in a hot alkaline, cleaning solution containing from 1%. to 5% of sodium hydroxide in order to preserve the clean surface.

The parts so cleaned are rinsed, in water and suspendedfrom the cathode" rod into a cadmium mercury alloy plating-solution of the following composition:

-Water 1 L.- 1 gal. Sodium cyanide G. 8 oz. Sodium hydroxide 15 G. 2 oz. Cadmium hydrate 15 G. 2 oz. Mercuric oxide 0.1 G. 0.0125 oz.

. Example [1.

T have found that apreferable method of stabilizing the cadmium and mercury contents of the bath is to use a cadmium mercury alloy anode to supply the desired quanion tities of these metals to the solution. A preferred composition of such an alloy is cadmium, 98%; mercury, 2%.

In plating for example steel fittings for aeroplane parts, I proceed as in Example I, with the exception that in this case, the above mentioned alloy anodes are used. A coating of similar analysis to that in Example I is obtained.

-In all the above examples the plating has been done in a still bath. It is understood that if mechanical solutions are used such as in barrel plating the concentrations of solutions, currents required, etc., may be changed considerably to conform to the different operating conditions.

The elimination of any single component of the ternary alloy described above and in the following claims gives a binary alloy deposit either superior to straight zinc deposits or cheaper than straight cadmium.

I do not claim specifically herein the novel products resulting from the processes and baths herein disclosed, as such products are claimed in another application Serial No.

' 684,507, filed January 5, 1924.

What I claim is:

1. In cadmium electroplating from a cyanide bath, the step which consists in depositing cadmium in the presence, of mercury to produce a coating of cadmium alloyed with a minor percentage of mercury. 2. Method of electroplating an alloy coating comprising cadmium and mercury which consists in makingthe-article to be plated the cathode and providing an anode comprising cadmium and mercury.

3. -Method of electrodepositing a cadmium alloy' which consists in making the article to be plated the cathode and providing an anode whose major constituent is cadmium the minor constituent being mercury.

4. Method of :electrodepositing a rust resistant deposit of cadmium and mercury which consists in electrodepositing these metals from a solution of their salts in an anide bath, the step which consists in depositing cadmium in the presence of a salt of mercury capable of resisting reduction by the bath toproduce a coating of cadmium alloyed with mercury.

7. In cadmium electroplating from a cyanide bath, the step which consists in depositing cadmium in the presence of a salt of mercury capable of resisting reduction by the bath to produce a coating of cadmium alloyed with a minor percentage of mercury.

'8. An anode for electroplating comprising cadmium and mercury in amounts effective for the purpose set forth.

9. An anode for electroplating comprising cadmium and about 2% of mercury. I

10. An anode for electroplating a major portion of which is cadmium and a minor port-ion is mercury.

Signed at Perth Amboy, in the county of 'Middlesex and State of New Jersey, this 28th day of December, A. D. 1923.

CHRISTIAN JOHN WERNLUND. 

